This invention relates to a process for reducing dust in fibrillated yarns, and more particularly, to a process for applying heat to said fibrillated yarns in order to reduce the dust particles.
In the formation of tape yarns of synthetic material by the fibrillation of film or tape, slitting or splitting the tape produces dust particles of the synthetic material in the form of fibrils and debris. The fibrils are thin fibers or threads having one of their ends attached to the tape yarn, either on the edges of the yarn or in the margins of the slit openings. The debris is broken or detached pieces or threads of the synthetic tape material remaining adhered to the surface of the tape yarn by static attraction, or in the form of loose dust particles detached from the tape yarn and settling on surrounding surfaces, such as parts of the fibrillating machine.
The fibrils and the debris statically attracted to the surface of the tape yarn, may remain on the tape yarn throughout subsequent yarn processing, or they may be separated by being broken off, knocked off or scraped off, during subsequent yarn processing steps, such as by reversal of movement of the tape yarn over yarn guides, or during winding or rewinding of the tape yarns about spindles or bobbins.
Furthermore, after the yarn, to which the dust particles adhere, are shipped to destinations in which the yarn is processed into fabrics, such as by weaving or knitting, such dust particles may be removed by the weaving apparatus or by the knitting apparatus, such as in the latches of the knitting needles. The resulting accumulation of dust particles upon the fabric processing machinery, such as the latches of the knitting needles, can jam or otherwise render inopertive such fabric processing parts, causing break-downs in the machinery, less efficient operation of the machinery, and/or fabrics of poor or unacceptable quality.
Several methods of reducing the occurrence of dust particles or removing the dust particles have been tried by the fibrillated yarn industry. One method is the blowing of air upon the yarns in order to remove the fibrils and debris. Another method is to mechanically brush the yarns after fibrillation to remove the dust particles. Another method, that has been tried, is to treat the fibrillated yarns with solvents in order to remove the dust particles. Yet another method is to treat the fibrillated yarns with water in order to wash the fibrils and debris from the yarns. Another method is electrostatic in nature to remove the dust particles from the yarns.
All of the above methods have met with limited or little success, and even those processes which are partially successful have other drawbacks, such as economics.
The applicants themselves first attempted to solve the problem of dust particle removal from fibrillated yarns by a method, which seemed obvious to them, of applying air-jet streams upon the in-line movement of the fibrillated tape yarns after fibrillation. Numerous experiments were conducted, including varying the spacing, number of air streams, angle of attack of air streams upon the moving in-line fibrillated tape yarns. However, such experiments removed only approximately 20 - 50 percent of the dust particles, a result which was unacceptable to customers, particularly in the knitting industry. Microscopic analyses of the air-treated fibrillated tape yarns revealed that dust particles in the form of attached fibrils tended to remain upon the tape yarns because the air jets were not sufficiently effective to remove such fibrils or to break them loose from the tape yarns. Increasing the pressure of the air improved the results of the dust particle removal from the fibrillated tape yarns, but such increased air pressure also created the problem of deflecting the tape yarns laterally in varying degrees away from their longitudinal in-line feeding direction. Such deflection could cause undue slack in the yarn, or tangling.
Another problem with a method of dust removal incorporating air streams of even the most efficient types, is that all such processes require a dust collection system in addition to the air projection system. Otherwise, the dust removed from the yarns would accumulate in other areas and other surfaces in the plant, creating additional problems of removing the dust from such other areas and surfaces.
It was also found that dust removal efficiency was increased by increasing the "yarn residence time" within the air jet stream. However the increased "yarn residence time" also subjected a greater length of the tape yarn to lateral deflection.
Although lateral deflection could be minimized by passing the yarn over a solid backing plate of some type, nevertheless the backing plate produces wear and abrasion upon the tape yarns as they move over the backing plate and are blown against the backing plate by the air jets.